Hyperbaric bupivacaine 0.5% is the most common drug used for a subarachnoid block (SAB) in India. The use is usually restricted for surgeries which require anesthesia from T-6 and below dermatome levels. Although 4 ml ampoules are in use for some time, the authors believe that more than 3 ml of bupivacaine is never really required for safe anesthesia for any surgery. In the current decade, the use of spinal additive drugs and combined spinal-epidural techniques is neither uncommon nor considered difficult to achieve good quality and prolonged analgesia or anesthesia. An epidural infusion via a catheter placed along with an SAB will provide adequate dermatome level, quality, and duration of anesthesia without the undesirable effects of a high spinal blockade.

This hypothesis cannot be complete without a quick review of the factors that affect the block height of an SAB. The most important factors include the baricity, the position of the patient, and the mass of the drug. [1] The height and weight of the patient do not have significant clinical effects on the dose of hyperbaric bupivacaine. A simple clinical derivation of this fact is that the block height increases by lowering the head end of the patient, keeping the mass and baricity of the drug constant. Injection site (L 2-3 vs. L 4-5) can also affect the level of block keeping the position of the patient constant. 15 mg or 3 ml of bupivacaine is the safe maximum mass of drug mentioned in most literature for a maximum achievable block height. [1]

The duration of a block depends mainly on the type of drug and can be increased, if required with the use of spinal additives such as opioids, α-2 agonists, etc., or an epidural add on. [2] Moreover, we know that a more extensive sympathetic block will cause more undesirable hemodynamic effects, [3] and therefore, it should be targeted to only the dermatomes necessary for the procedure. A large dose (volume) cannot ensure low dermatome blockade in any patient position.

The authors tried to analyze the difference in the cost factor if bupivacaine was made available in 3 ml instead of a 4 ml ampoule. We checked the records in our multispecialty tertiary hospital in the last 1 year. 2566 SAB were administered out of which ≤3 ml bupivacaine was used in 99.65% of the cases. The cost of one commercially available ampoule is not prohibitive, but the collective cost of ≥1 ml being wasted in a large number of SAB may be significant. Other relevant factors affecting the cost (like intravenous fluids/vasopressors or epidural set/spinal additive drugs) however, limits the strength of our hypothesis.

So, is there is the need to administer more than 3 ml of 0.5% hyperbaric bupivacaine in any patient! Is it not safer to use an epidural or an additive drug along with the spinal block! Why should it be marketed for regular use in a 4 ml ampoule at all!